What is Sour Beer?

Sour beers, or those that include bacteria as part of the fermentation process have recently become extremely popular amongst craft breweries in the US.  And while this might seem like a new trend, beers with sour flavors caused by bacteria are actually an ancient art that has recently found new life. 

Humans have been brewing beer for roughly 9,000 years according to the archaeological record, and for most of that time there was no real understanding of microbiology.  Ancient brewers knew how to control their fermentations, but the exact mechanics of what was happening inside their vats was essentially unknowable. 

During fermentation, brewers’ yeast consumes sugar and produces alcohol and carbon dioxide.  And while these members of the saccharomyces genus are the yeast brewers want in their tanks to produce beer, wild yeast and bacteria are also all around us all the time.  When bacteria consume sugars, they typically produce acids, and these acids stick around as sour flavors in the finished beer. 

In ancient times, it would have been nearly impossible for brewers to keep all bacteria out of their beer.  They didn’t know the stuff existed, so how could they prevent it?  Through careful aging and blending of different batches of beer, brewers sought instead to control the acidity in their finished products and make tart refreshing beers in which sourness was a desirable component. 

As technologies and information improved, however, the sour flavors caused by bacteria came to be seen as a fault, and the world moved toward the “clean” beers we enjoy today.  However, in certain little pockets around the world this old tradition continued.  Over the past ten years or so, American craft brewers have rediscovered these old beer-making techniques and have begun to incorporate bacteria into some of their batches of beer. 

For most people, that first sip of a sour beer is a bit of a shock.  These beers have flavors that aren’t commonly associated with “beer”, so most people have a moment of surprise and confusion.  But, don’t let that initial shock be a deterrent.  After a couple of small sips, the strangeness fades away and the true flavors of the beer begin to shine. 

If you’d like to learn more about sour beers, sign up for one of our brewery tours!